Opportunities for selection to improve steer and cow productivity in northern Australia

This thesis analysed carcass records from 2180 tropically adapted, steers (986 Brahman (BRAH) and 1194 Tropical Composite (TCOMP)) describing weight, eye muscle area, P8 and 12/13th rib fat depth, percent intramuscular fat and retail beef yield, with tenderness assessed as shear force. All steers were feedlot finished with a subset (680 BRAH and 783 TCOMP) recorded for individual feed intake. Female reproductive performance in the half-sib sisters of these steers (1007 BRAH and 1108 TCOMP) was evaluated as outcomes of their first (Mating 1: when females averaged 27 months of age) and second (Mating 2) annual matings, and averaged over up to 6 matings (termed 'lifetime' reproduction traits). Heifer and cow weight, eye muscle area, P8 and 12/13th rib fat depth, body condition score and hip height were recorded at 18 months of age, immediately prior to first calving and at Mating 2. The maternal genetic component of weaning weight (Maternal WWT) was estimated based on weaning weight records available for these steers and females and the progeny of females (N = 12528)

Ellagic Acid Derivatives from Rubus ulmifolius Inhibit Staphylococcus aureus Biofilm Formation and Improve Response to Antibiotics

Biofilms contribute to the pathogenesis of many forms of Staphylococcus aureus infection. Treatment of these infections is complicated by intrinsic resistance to conventional antibiotics, thus creating an urgent need for strategies that can be used for the prevention and treatment of biofilm-associated infections.This study demonstrates that a botanical natural product composition (220D-F2) rich in ellagic acid and its derivatives can limit S. aureus biofilm formation to a degree that can be correlated with increased antibiotic susceptibility. The source of this composition is Rubus ulmifolius Schott. (Rosaceae), a plant used in complementary and alternative medicine in southern Italy for the treatment of skin and soft tissue infections. All S. aureus clonal lineages tested exhibited a reduced capacity to form a biofilm at 220D-F2 concentrations ranging from 50-200 µg/mL, which were well below the concentrations required to limit bacterial growth (530-1040 µg/mL). This limitation was therapeutically relevant in that inclusion of 220D-F2 resulted in enhanced susceptibility to the functionally-distinct antibiotics daptomycin, clindamycin and oxacillin. Testing with kidney and liver cell lines also demonstrated a lack of host cell cytotoxicity at concentrations of 220D-F2 required to achieve these effects.These results demonstrate that extract 220D-F2 from the root of Rubus ulmifolius can be used to inhibit S. aureus biofilm formation to a degree that can be correlated with increased antibiotic susceptibility without toxic effects on normal mammalian cells. Hence, 220D-F2 is a strong candidate for development as a botanical drug for use in the prevention and treatment of S. aureus biofilm-associated infections

The impact of genetic markers for tenderness on steer carcass and feedlot exit and heifer puberty traits in Brahman cattle

Four genetic markers (T1, T2, T3 and T4) have been shown to have a significant effect on tenderness (measured as shear force) in Brahman cattle. This study examined the relationship between tenderness markers and steer (N = 940) feedlot exit and carcass, and heifer (N = 973) puberty traits. For most traits assessed, tenderness markers had no significant effects. Differences in T1 genotype, however, significantly (

Shorthorn trial Net Feed Intake (NFI) EBV

Net feed intake (NFI) is a trait developed to describe differences between animals for feed efficiency. NFI is defined as the difference between the feed eaten by an animal and that expected to have been eaten given the animal’s weight and gain during a 70-day test period. A lower (more negative) NFI record reflects a more feed efficient animal (i.e. an animal eating less given its weight and gain). BREEDPLAN has been calculating a NFI EBV since 2003 for the Angus and Hereford breeds. The Durham R&D project has been collecting NFI records for several years on subsets of the domestic finished cattle. These records, along with those from the BEEF CRC1, have now been used to compute NFI EBVs for Shorthorn. Given the limited number of records these EBV have to be considered as trial EBVs only

Effects of early weaning on growth, feed efficiency and carcass traits in Shorthorn cattle

This study aimed to examine the impact of early weaning on residual feed intake, and other production and carcass traits, in a group of cattle subjected to early or conventional weaning treatments, but otherwise managed as contemporaries. Shorthorn (n = 140) calves were randomly allocated by sex and sire to early and conventional weaning treatments. Early weaned animals (n = 69) were weaned at an average of 123 days of age and 145 kg liveweight, while conventionally weaned steers and heifers (n = 71) were 259 days old at weaning and 273 kg. Following conventional weaning, animals were managed as contemporaries through backgrounding, and entered feedlot finishing at a mean age of 353 and 408 days for heifers and steers, respectively, for finishing and feed intake testing. At the conclusion of feed intake testing hip height was measured, and animals were ultrasound scanned to assess fat depth, eye muscle area and percent intramuscular fat. Early weaned animals were significantly lighter (

Modeling the relationship between scanned rump and 12th-rib fat in young temperate and tropical bovines: Model development and evaluation

A decision support tool for predicting subcutaneous fat depths called BeefSpecs, based on the Davis growth model (DGM), has been developed by the Cooperative Research Centre for Beef Genetic Technologies. Currently, the DGM predicts 12th-rib fat thickness (RFT, mm). To allow predictions of fat thickness at the P8 rump (P8FT, mm) site, the standard carcass fat measurement in the Australian beef industry, a relationship was developed between ultrasound RFT and P8FT in steers and heifers from temperate (Angus, Hereford, Shorthorn, and Murray Grey) and tropical (Brahman, Belmont Red, and Santa Gertrudis) breed types. Model development involved fitting various combinations of sex, breed type (BrT), BW, age, and RFT to produce 6 models. The models were challenged with data from 3 independent data sets: 1) Angus steers from 2.4 generations of divergent selection for and against residual feed intake; 2) 2 tropically adapted genotypes [Brahman and tropically adapted composites (combinations of Belmont Red, Charbray, Santa Gertrudis, Senepol, and Brahman breeds)]; and 3) a study using sires from Charolais, Limousin, Belgian Blue, and Black and Red Wagyu breeds and 3 genetic lines of Angus to create divergence in progeny in terms of genetic potential for intramuscular fat percent and retail beef yield. When challenged with data from Angus cattle, the mean biases (MB, mm) for models A to F were –1.23, –0.56, –0.56, –0.02, 0.14, and 0.04, and the root mean square errors of predictions (mm) were 1.53, 0.97, 0.97, 0.92, 0.93, and 0.91, respectively. When challenged with data from Brahman cattle, MB were 0.04, –0.22, –0.14, 0.05, –0.11, and 0.02 and root mean square errors of predictions were 1.30, 1.29, 1.27, 1.23, 1.37, and 1.29, respectively. Generally, model accuracy indicated by MB tended to be less for model E, which contained age rather than BW as a covariate. Models B and C were generally robust when challenged with data from Angus, Brahman, and Tropical Composite cattle as well as crossbred cattle with temperate sires. Model D, which did not contain age, performed the most consistently and was selected for inclusion in the DGM: P8FT, mm = –3.6 (±0.14) + 1.3 (±0.13) x sex + 0.11 (±0.13) x BrT + 0.014 (±4.8E–⁴) x BW + 0.96 (±0.01) x RFT – 0.73 (±0.08) x sex x BrT – 3.8E–³ (±4.2E–⁴) x sex x BW – 0.09 (±0.01) x sex x RFT + 1.3E–³ (±3.7E–⁴) x BrT x BW + 0.24 (±0.01) x BrT x RFT (adjusted R² = 0.86; SE = 0.013). Model D has been implemented in BeefSpecs to predict P8FT

Genetics of meat quality traits in two tropically adapted genotypes of beef cattle: 1. Genetic parameters and correlations

Meat quality traits are instrumental in determining consumer satisfaction with beef meat products, and in defining the value of carcasses. Measurements of tenderness (as peak force: PF and compression: CMP), percent cooking loss (CLoss), meat color (ColL) and percent intramuscular fat (IMF) were recorded for meat samples from 2178 feedlot finished tropically adapted steers of two genotypes (Brahman: BRAH and Tropical Composite: TCOMP). Tenderness traits were moderately heritable in BRAH (PF = 0.33; CMP = 0.19) and TCOMP (PF = 0.32; CMP = 0.20). CLoss, ColL and IMF traits were more heritable in TCOMP (0.22, 0.42 and 0.60 respectively) than BRAH (0.09, 0.20 and 0.42 respectively). Genetic correlations between meat quality traits indicated that selection for individual traits would not negatively impact other meat quality measures. The genetic relationships between ColL and PF in BRAH, and between ColL and CMP, and IMF and CMP in TCOMP, suggest that opportunities may exist for indirect selection for tenderness in tropically adapted cattle

Genetics of meat quality traits in two tropically adapted genotypes of beef cattle: 2. Influence of tenderstretching

Tender stretching (TS) is an alternative means of hanging beef carcasses which, when compared to sides conventionally hung by the Achilles tendon (AT), minimises the potential for muscle shortening during rigor in the high priced cuts of the rump and loin. A total of 1,939 tropically adapted steers of two genotypes (889 Brahmans (BRAH) and 1,050 Tropical Composites (TCOMP)) were used to estimate the effect of TS on the genetic parameters of meat quality traits. Measurements of meat quality traits (peak force (PF), cooking loss (CLoss) and compression (CMP)) were performed on feedlot finished steers. Heritabilities of meat quality traits were moderate in both genotypes. For BRAH heritability estimates were 0.33, 0.15 and 0.07 for PF, CMP CLoss, respectively. The heritabilities for TCOMP were 0.30, 0.27 and 0.21, respectively. Use of TS resulted in a proportional reduction in phenotypic and additive variances in comparison to conventionally hung carcases. As a result, the heritabilities of TS meat quality traits are similar to those measured on conventionally hung carcases. Despite this, the response to selection upon TS measurements will be significantly reduced, in comparison to AT, due to the reduction in additive variance. However, the reduced phenotypic variances for TS measurements suggest that commercial use of TS in the abattoir will lessen the need to select for tenderness in beef genetically

Genetics of steer daily and residual feed intake in two tropical beef genotypes, and relationships among intake, body composition, growth and other post-weaning measures

Genetic parameters for Brahman (BRAH) and Tropical Composite (TCOMP) cattle were estimated for steer production traits recorded at weaning (WEAN), 80 days post-weaning (POSTW), feedlot entry (ENTRY) and after ~120 days feedlot finishing (EXIT). The TCOMP was 50% 'Bos indicus', African Sanga or other tropically adapted 'Bos taurus', and 50% non-tropically adapted 'Bos taurus'. Data involved 2216 steers, comprising 1007 BRAH by 53 sires and 1209 TCOMP by 50 sires. Individual daily feed intake (DFI) and residual feed intake (RFI) were assessed on 680 BRAH and 783 TCOMP steers over an ~70-day feedlot test. Other traits were liveweight (LWT), average daily gain (ADG), ultrasonically scanned rump (SP8) fat depth, rib (SRIB) fat depth, 'M. longissimus' area (SEMA) and intra-muscular fat % (SIMF), body condition score (CS), hip height (HH), flight time (FT) and serum insulin-like growth factor-I concentration (IGF-I). BRAH were significantly (

Genetics of growth and feed efficiency

The CRC for Cattle and Beef Quality was established in 1993 to identify the genetic and non-genetic factors affecting beef quality and other production traits of economic importance. Providing feed for cattle is the single largest input cost in beef production enterprises. Advances in computing and electronics has allowed the development of reliable automatic feed intake recorders making it easier to measure feed intake, and this in association with increased producer demand for a means of selecting on the basis of efficiency, has led to increased research in feed efficiency. Understanding genetic variation in feed efficiency and providing the tools for genetic improvement in the efficiency of feed utilization can have a major impact on profitability. Progress of research within the CRC, and internationally, for beef cattle feed efficiency has been regularly reviewed and published (Archer et al. 1999; Herd et al. 2003a; Arthur et al. 2004; Arthur and Herd 2005, 2006). This paper summarises the CRC's major contributions to new knowledge and applications for genetic improvement of growth and feed efficiency